Refurbish G8 belt grinder platen

Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.

Moderators: GlennW, Harold_V

User avatar
BadDog
Posts: 5131
Joined: Wed May 17, 2006 8:21 pm
Location: Phoenix, AZ

Refurbish G8 belt grinder platen

Post by BadDog »

I have a 5 HP Porter Cable G8 belt grinder that was manufactured 80 years ago. After all that time, it's in amazing condition, except for wear on the platen, which is something I would like to improve.

The platen itself is a piece of 18.75" x 9" x 1/2" hardened steel bolted to a beefy casting, and has worn several concavities in it's surface. The whole thing is symmetrical, allowing it to be flipped to put fresh surface at the table. Sadly, that appears to have been done in the past. And it can't be flipped front to back because of the countersunk screws for mounting. So it's going to have to have some effort to improve.

My first thought would be to send it out to get ground (probably Blanchard). Then I thought, maybe I can upgrade with modern materials? My first thought was maybe machine a sort of frame/holder for replaceable PTFE wear surface. Not sure how hot it gets on the back side of those heavy 36 grit (typical) Zirconia belts, or if that would even be a problem.

A bit of searching seems to indicate that the KMG guys like the "ceramic glass" (clear ceramic) platens, and price for purchasing such a panel seems like it will be cheaper than having it ground flat. That would still require some sort of mounting frame (just lip at bottom?). Perhaps with plate glued on, then using heat to break the bond should replacement become necessary?

I don't expect the volume of the usage I would put it through will ever result in another worn out platen to replace should it simply be ground, and I haven't gotten prices yet, so just kicking around ideas.
Russ
Master Floor Sweeper
User avatar
NP317
Posts: 4557
Joined: Tue Jun 24, 2014 2:57 pm
Location: Northern Oregon, USA

Re: Refurbish G8 belt grinder platen

Post by NP317 »

I like your thinking of new materials for the replacement platen, although I am not sufficiently knowledgeable to make a recommendation.
RussN
pete
Posts: 2518
Joined: Tue Feb 10, 2009 6:04 am

Re: Refurbish G8 belt grinder platen

Post by pete »

I've no idea of cost but it shouldn't be hard to check. One other option would be what's commonly used in open pit tailings lines are hardened stainless steel gate valves. They come in a wide variety of sizes and thicknesses to well above what you'd need. Visualize a hardened and ground flat plate with a radius at one end. If there durable in that environment it's doubtful you'd ever wear one out. I know the plates are available separately and without the rest of the valve components.
Mr Ron
Posts: 2126
Joined: Tue Dec 22, 2009 12:36 pm
Location: Vancleave, Mississippi

Re: Refurbish G8 belt grinder platen

Post by Mr Ron »

According to my calculations, that platen weighs in at close to 24 pounds. Shouldn't be too hard to get another piece of 1/2" plate and replace the old platen. A Blanchard grind is not necessary for that platen as it is not used to produce precision work. It's use is to remove a lot of material quickly. BTW, is that machine 3 ph? Nice machine!
Mr.Ron from South Mississippi
User avatar
BadDog
Posts: 5131
Joined: Wed May 17, 2006 8:21 pm
Location: Phoenix, AZ

Re: Refurbish G8 belt grinder platen

Post by BadDog »

pete:
Thanks. That's not something would ever have crossed my mind! Exactly why I posted.

Mr Ron:
Yes, it's quite heavy, particularly when attached to it's massive casting. And I realize that the platen isn't a precision surface, but the grinder angle is to deal with it's rather extreme hardness. I pondered cutting it with a fly cutter using a carbide bit. But wondered if the less than polished surface would cause wear/heat in the belt. Of course it could be worked with sandpaper to a finer finish, but the thought of surface plate sanding a plate that big and heavy took my thoughts back to grinding.

And yes, it is 3ph. She's a beast!
Russ
Master Floor Sweeper
JackF
Posts: 1616
Joined: Mon Jan 26, 2009 3:56 pm
Location: Caldwell, Idaho

Re: Refurbish G8 belt grinder platen

Post by JackF »

I for one would like a pic of this beast. :D :D I love old machinery. :D :wink:

Jack
User avatar
neanderman
Posts: 896
Joined: Mon Jan 09, 2012 7:15 pm
Location: Cincinnati, Ohio, USA

Re: Refurbish G8 belt grinder platen

Post by neanderman »

JackF wrote: Mon Jul 19, 2021 8:24 pm I for one would like a pic of this beast. :D :D I love old machinery. :D :wink:
Second that!
Ed

LeBlond Dual Drive, 15x30
US-Burke Millrite MVI
Atlas 618
Files, snips and cold chisels

Proud denizen of the former "Machine Tool Capitol of the World"
User avatar
Bill Shields
Posts: 10460
Joined: Fri Dec 21, 2007 4:57 am
Location: 39.367, -75.765
Contact:

Re: Refurbish G8 belt grinder platen

Post by Bill Shields »

You want the platen surface to be as smooth as possible
Too many things going on to bother listing them.
User avatar
BadDog
Posts: 5131
Joined: Wed May 17, 2006 8:21 pm
Location: Phoenix, AZ

Re: Refurbish G8 belt grinder platen

Post by BadDog »

Sorry, I'm terrible about taking pictures. And just didn't have time to try to make them small enough for the site to allow them. But, here you go. Not real interesting, but you can see the machine and the platen removed. I included a 123 block for scale.
g8-1.jpg
g8-3.jpg
g8-2.jpg
Russ
Master Floor Sweeper
User avatar
BadDog
Posts: 5131
Joined: Wed May 17, 2006 8:21 pm
Location: Phoenix, AZ

Re: Refurbish G8 belt grinder platen

Post by BadDog »

You may notice it still sits on rickety casters. Making a good pallet jack suitable base is "on the todo list"...
Russ
Master Floor Sweeper
LIALLEGHENY
Posts: 363
Joined: Sat Jan 11, 2014 12:36 am
Location: Bohemia, NY

Re: Refurbish G8 belt grinder platen

Post by LIALLEGHENY »

BadDog,

I have a pair of Porter Cable B9 belt grinders that could stand to have the platens redone, so I will be curious as to what you do. These had new platens brazed on at some point in their lifetime. Great heavy duty pedestal type machine that has a quick release tensioned top roller . You can change a belt in under a minute without any fussing.

Nyle
User avatar
GlennW
Posts: 7284
Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Refurbish G8 belt grinder platen

Post by GlennW »

What about just use a piece of 1/2" steel tooling plate. It comes Blanchard ground.

I'm sure you could find a drop somewhere.

It may not wear as well as what you have, but you may not be needing it eighty years from now!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
Post Reply